Median AQI
47
Good
Colorado · County air quality · 2025
Mesa County, Colorado
Median AQI 47 (Good). 67.4% of monitored days rated Good, direct from EPA Air Quality System stations.
- 47
- Median AQI
- 67.4%
- Good-air days
- 0
- Unhealthy days
- 27%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Mesa County's air is good on balance, more polluted than the median US county, a median AQI of 47 with 67.4% of 273 monitored days in the Good band, driven mainly by Ozone.
- 47
- median AQI · Good
- 67.4%
- days rated Good
- Ozone
- main pollutant
- 27%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 90.
Data updated July 2026
- Good · 184 d · 67.4%
- Moderate · 89 d · 32.6%
How did Mesa County's air break down in 2025?
Across 273 monitored days, 184 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 90 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 47 (Good).
Insights: Mesa County, Colorado. EPA monitors recorded a median Air Quality Index of 47 across 273 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 184 (67%) fell in the Good band (AQI 0–50), 89 (33%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 64, while the worst single-day peak hit 90 (Moderate). Residents averaged about 20.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (224 days), PM2.5 (49 days). Across the 2020–2025 trend window, good days shifted by -78 and the median AQI moved +3 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 90, moderate but never Unhealthy. Nearby counties show comparable readings: Adams (50.2% good, AQI 50); Alamosa (90.8% good, AQI 24); Arapahoe (47.3% good, AQI 51); Archuleta (79.5% good, AQI 32); Boulder (50.9% good, AQI 50); Clear Creek (64.4% good, AQI 48).
Air Quality Summary
Good Days
67.4%
184 of 273 monitored days
-7.6pp vs 75% target
Max AQI Recorded
90
Moderate
Health Grade
Moderate
90th-pct AQI 64
Mesa County, Good days share 67.4%
National avg
Share of monitored days at AQI 0-50 (Good band).
Mesa County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 273 monitored days across EPA AQI categories.
Good
184
67%
Moderate
89
33%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Mesa County.
- Ozone · 224 days · 82.1%
- PM2.5 · 49 days · 17.9%
Health Impact Assessment
Moderate
Mesa County's air quality is rated Moderate based on 67.4% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 67.4% of monitored days in 2025, with a median AQI of 47. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 224 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Mesa County. Best year: 2022 (282 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 262 | 101 | 3 | 0 | 44 | 108 |
| 2021 | 247 | 116 | 2 | 0 | 46 | 139 |
| 2022 | 282 | 82 | 1 | 0 | 44 | 108 |
| 2023 | 246 | 119 | 0 | 0 | 46 | 90 |
| 2024 | 215 | 144 | 7 | 0 | 48 | 136 |
| 2025 | 184 | 89 | 0 | 0 | 47 | 90 |
How does Mesa County compare?
How Mesa County compares
Good-day share worse than US avg
Mesa County 67.4%
Adams County, Colorado 50.2%
US average 76.5%
Median AQI worse than US avg
Mesa County 47
Adams County, Colorado 50
US average 38
Unhealthy days / yr about average
Mesa County 0
Adams County, Colorado 0
US average 0
Other Counties in Colorado
Air quality comparison for nearby counties in Colorado.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Mesa County.
Beaver County, Pennsylvania
AQI 47 · 54.3% good
Bell County, Texas
AQI 47 · 61.3% good
Bowie County, Texas
AQI 47 · 57.3% good
Bronx County, New York
AQI 47 · 56.6% good
Butte County, California
AQI 47 · 66.1% good
Calcasieu County, Louisiana
AQI 47 · 61.5% good
What Mesa County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 47 means for exposure. Health guidance
- See how Mesa County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Mesa County with its Colorado neighbours before drawing a conclusion about the region. All of Colorado
Based on 273 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Mesa County, Colorado? ▼
Mesa County has a median Air Quality Index (AQI) of 47, rated "Good." 67.4% of monitored days (184 out of 273) had good air quality in 2025.
What is the main pollutant in Mesa County? ▼
The primary pollutant in Mesa County is Ozone (O3), which was the main AQI driver on 224 days (82% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Mesa County have? ▼
In 2025, Mesa County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 90.
Is the air quality in Mesa County getting better or worse? ▼
Air quality in Mesa County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 282 good days. Worst year: 2025 with 184 good days.
What does AQI 47 mean for health? ▼
Mesa County's median AQI of 47 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Mesa County compare to other counties in Colorado? ▼
Mesa County has 67.4% good air days. Nearby counties in Colorado: Adams (50.2% good), Alamosa (90.8% good), Arapahoe (47.3% good), Archuleta (79.5% good), Boulder (50.9% good), Clear Creek (64.4% good).
What is the 90th percentile AQI in Mesa County? ▼
The 90th percentile AQI for Mesa County is 64, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 90 (Moderate).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.